Rail transportation is generally recognized as being more economical than truck transportation for bulk commodities such as aggregates. Large quantities of such commodities can be moved by a small crew at low costs. However, rail transportation frequently loses out in competitive situations because of the cost of unloading, stockpiling, and delivering the commodity to the ultimate destination.
Even though large quantities of bulk material can be transported at low costs from one terminal to another, the burden is placed on the unloading facility to maintain the economics of this method of transportation for the purchaser of the commodity. Even if the unloading is slow, the train is therefore delayed for a substantial period of time for the unloading to be accomplished, there is an added investment cost per ton handled for the use of the railroad equipment. One problem, in this regard, is that rail transportation is a twenty-four (24) hour operation while many of the industries it serves operate only during daylight hours. Often, a train makes good speed from origin to destination, only to be delayed several hours waiting to be unloaded Each hour of delay adds to the transportation costs as much as an additional twenty-five (25) miles of haul.
As an example of the efficiency of rail transport for bulk commodities, a train with a two-man crew pulling 1600 net tons at 55 miles per hour would be producing 32 times as many ton-miles per hour as a dump truck driver hauling 25 tons at 55 miles per hour.
Another problem affecting the efficiency of rail transportation for bulk commodities is that, under current methods, the quick unloading of a commodity train requires high capacity equipment and facilities which are idle most of the time. Such high-capacity equipment and facilities are expensive and add significantly to the investment costs per ton handled.
It is important for rail transportation of bulk commodities to offer ease of unloading and ease of transportation. This is particularly the case where aggregates and bulk material having a particle size ratio of over six are involved. (A particle size ratio of six means that the largest particles are no more than six times the size of the smallest particles.) Also, the amount of load that can be carried by the rail transportation system is a function of the center of gravity of the load. If the center of gravity of the load is too high, than less material can be carried. A high center of gravity will enhance the risk of derailing and/or toppling of hopper cars. Additionally, hopper cars that have relatively shallow walls and relatively small discharge openings will create difficulties when the material is desired to be discharged. With certain types of materials, the shallow walls will cause a "bridging" effect with the material within the hopper cars. Thus, it becomes difficult to unload the hopper car when the hopper car reaches the destination site.
There are many methods that are currently used for the unloading of bulk materials from trains. For example, bottom dumping hopper cars are equipped with automatic doors that are opened automatically as the cars move over a pit, where the pit facility includes a feeder and a conveyor. Either a pit or an elevated trestle is required for this method, so that this method is ruled out at many locations. Obviously, the providing of a pit or trestle facility with associated conveyor systems is expensive.
Another method involves the use of rotary car dumpers. These are commonly used for unloading coal at electric generated plants. Once again, the equipment for unloading the cars is highly specialized and expensive.
Side dumping cars have been used for many years. These side dumping cars, however, cannot be dumped on level ground. They require an elevated track on a built-up embankment, for example, so that the dumped material will flow over the side of the embankment an not flow back over the track.
In addition, backhoes or other unloading equipment are used to unload standard gondola cars. These methods are generally slow, promoting the delay problems mentioned above.
A significant development in the unloading of hopper cars occurred with the invention of U.S. Pat. No. 4,925,356, issuing on May 15, 1990 to the present inventor and to William B. Snead. U.S. Pat. No. 4,925,356 disclosed a self-unloading train for the transfer of bulk materials that comprises a plurality of hopper cars, a train conveyor, and a gating system. The plurality of hopper cars are coupled together to form a train Each hopper car has at least one hopper having walls inclined at shallow angles to the vertical and a bottom discharge opening having a width at least 50% of the distance between the wheels of the hopper cars. The train conveyor is an endless belt supported on the cars and underlying each of the hopper discharge openings. This endless belt receives the material discharged from the hopper discharge openings. The train conveyor extends the length of the plurality of hopper cars. The train conveyor has a width that is substantially greater than the width of the discharge openings. The gating systems are operable selectively so as to discharge material from the hoppers onto the train conveyor. In particular, these gating systems are made up of clam shell-type gates that are pivoted about the axis parallel to the train conveyor. These clam shell-type gates assist in controlling the flow of material onto the train conveyor.
The trailer car of this self-unloading train of U.S. Pat. No. 4,925,356 is positioned at the end of the plurality of hopper cars. The train conveyor extends to the trailer car. This trailer car supports a lift portion of the train conveyor at its discharge end sufficiently high to discharge the material to a transfer conveyor. This transfer conveyor is mounted on the trailer car so as to receive material from the train conveyor and to discharge the material at selected points surrounding the trailer car.
Each of the hopper cars of this invention has a center sill. The return run of the conveyor belt is supported by split return idlers disposed along each side of the center sill. The supply run of the conveyor belt is supported by catenary troughing idlers disposed immediately above the return run. A suitable drive system is provided for the train conveyor and the transfer conveyor. This drive system includes electric drive motors for the conveyor, a generator for providing electric power to the drive motors, and an internal combustion engine for driving the conveyor.
The actual embodiment of U.S. Pat. No. 4,925,356 has been very successful in actual operation. After extended use, it was found that this "Dump Train" should normally be unloaded on straight sections of track. Since the Dump Train has a substantial length, it was found that a restriction to the use of the Dump Train was that it must be unloaded on straight sections of track. If the train was unloaded on a curved section of track, then a great deal of deflection and distortion of the conveyor belt would occur. Any deflection or distortion of the conveyor belt, because of the curvature of the track, could minimize the effectiveness of the Dump Train and could cause extensive wear and damage to the conveyor belt. In many areas of the country, and in many desired unloading locations, it was found that straight sections of track were not readily available. As such, a need developed for enabling the Dump Train to be unloaded on curved sections of track. This would add greatly to the effectiveness of the Dump Train concept, would open up many more markets for the Dump Train, and would allow the Dump Train to be increasingly flexible to the needs of the user.
In the past, there has not been great experimentation with conveyor belts for traversing curves. Except in the specialized application of the Dump Train, it is much simpler for conveyor designers to design straight sections of conveyor belt which discharge onto adjacent straight sections of conveyor belt. There has seldom been a need for designing a curved section of conveying equipment.
Another problem with the Dump Train has been the cost of the transfer car. It is an expensive proposition to place a lift conveyor, and a transfer conveyor, on a single railroad car. In addition, a great deal of cost is required for the hydraulic system and power system for the operation of the transfer conveyor. The transfer conveyor also adds weight to the train. The tonnage of cargo that can be carried legally by a train would be offset by the weight of the transfer conveyor.
There are many locations, where material must be delivered, that already have suitable portable conveyor systems available. In many instances, it is only necessary to lift the material and to "dump" the material into an adjacent railroad car. As such, a need exists for presenting an economy version of the transfer car of the Dump Train which in particular eliminates the need for the large transfer conveyor.
The Dump Train utilizes a hopper car having four hoppers contained therein The Dump Trains is generally made up of ten hopper cars which extend for a considerable length. In many locales throughout the United States, it can be difficult to find such a long straight section of track so as to accommodate the full operation of the Dump Train. This is particular true when it is necessary to unload the Dump Train in remote locations where aggregate material for construction and maintenance purposes may be needed. As such, it was felt necessary to build a self-unloading train in which the cars are shorter and the conveyor belt could be trained so as to accommodate such curves.
The transfer car of the Dump Train includes a large amount of hydraulic and electrical equipment. The electrical equipment is utilized so as to power the conveyor system for the purpose of unloading the train. Since the Dump Train and the associated conveyor system are relatively large, a great deal of power is required. Unfortunately, the electrical equipment used on the transfer car of the Dump Train is quite heavy. Throughout the operation of the Dump Train, it is necessary for the Dump Train to carry along its own power supply. Therefore, it was felt desirable to provide a self-unloading train that could be actuated by external power systems. The minimization of weight also enhances the ability of the self-unloading train to carry a greater amount of cargo.
The Dump Train has been of a generally standard size. However, many users desire to have different sizes of trains depending on the type of job in which the train is employed. Many aggregate transportation jobs require only the capacity of a few of the available hopper cars. If the Dump Train were employed in such a setting then it would needlessly require the transport of unfilled cars. On the other hand, many jobs require much more aggregate material than could be conveniently carried in a single load of the Dump Train. In such a circumstance, it would be desirable to be able to add additional cars to the self-unloading train design so as to accommodate the entire amount of aggregate material required for a particular job. As such, it was felt desirable to have flexibility in the size and design of the self-unloading train.
It is an object of the present invention to provide a self-unloading train that is suitable for discharging material from curved sections of track.
It is another object of the present invention to provide a conveyor guide system that resists deflection and distortion of the conveyor belt when operating on curves.
It is another object of the present invention to provide a conveyor guide system that can be easily adapted for use on self-unloading trains
It is still a further object of the present invention to provide a conveyor guide system for a self-unloading train that is economical and easy to operate.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.